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Groups > comp.lang.python > #80093

Re: Classes

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On Fri, 31 Oct 2014 19:32:13 -0400, Seymore4Head
<Seymore4Head@Hotmail.invalid> declaimed the following:

>
>class Rectangle(object):
>    def __init__(self, length, width=None):
>        self.length = length
>        if width is None:
>            self.width = length
>        else:
>            self.width = width
>    def area(self):
>        return self.length * self.width
>    def perimeter(self):
>        return 2 * (self.length + self.width)
>
>class Square(Rectangle):
>    def area(self):
>        return self.length * self.width
>    def perimeter(self):
>        return 2 * (self.length + self.width)    
>
	Why did you redefine area and perimeter? Those are supposed to be
inherited operations from Rectangle. You've duplicated what should not have
been changed, and removed everything that makes a Square a Square.

	The "assignment" was to create a Square class that enforces the
property of "squareness" (length = width, or a simple "side").

	What you created does not do that.
    
>a=Rectangle(3,5)
>print (a.area())
>print (a.perimeter())
>b=Rectangle(5,7)
>print (b.area())
>print (b.perimeter())
>c=Square(4)
>print (c.area())
>print (c.perimeter())

	You're tests ignore the case of /changing/ side/length/width...
Consider what happens if you execute

c.length = 5
c.width = 9

	Your "square" is now a rectangle... My example forces every change to a
"Square" to affect both dimensions equally -- no matter if you set .side,
.length, .width, the square will still be a square.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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Classes   Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-30 16:16 -0400
  Re: Classes sohcahtoa82@gmail.com - 2014-10-30 13:33 -0700
    Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-30 17:00 -0400
  Re: Classes Rob Gaddi <rgaddi@technologyhighland.invalid> - 2014-10-30 13:34 -0700
    Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-30 17:00 -0400
  Re: Classes Larry Hudson <orgnut@yahoo.com> - 2014-10-30 14:28 -0700
    Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-30 17:34 -0400
      Re: Classes sohcahtoa82@gmail.com - 2014-10-30 18:21 -0700
      Re: Classes alister <alister.nospam.ware@ntlworld.com> - 2014-10-31 09:59 +0000
        Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 10:07 -0400
  Re: Classes   "ast" <nomail@invalid.com> - 2014-10-31 10:05 +0100
    Re: Classes   "ast" <nomail@invalid.com> - 2014-10-31 10:18 +0100
      Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-10-31 20:21 +1100
    Re: Classes   Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 10:05 -0400
      Re: Classes Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-31 08:47 -0600
        Re: Classes Grant Edwards <invalid@invalid.invalid> - 2014-10-31 15:49 +0000
          Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 12:31 -0400
            Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-11-01 03:37 +1100
              Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 12:47 -0400
                Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-11-01 04:02 +1100
                Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 13:31 -0400
                Re: Classes Zachary Ware <zachary.ware+pylist@gmail.com> - 2014-10-31 12:39 -0500
                Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 13:57 -0400
                Re: Classes Rob Gaddi <rgaddi@technologyhighland.invalid> - 2014-10-31 10:40 -0700
                Re: Classes Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-11-01 11:17 +1300
                Re: Classes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-01 12:06 +1100
                Re: Classes Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-01 00:12 -0600
                Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-11-01 17:32 +1100
                Re: Classes Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-11-03 00:32 +1300
            Re: Classes Dave Angel <davea@davea.name> - 2014-10-31 13:20 -0400
            Re: Classes Marko Rauhamaa <marko@pacujo.net> - 2014-10-31 19:35 +0200
            Re: Classes Grant Edwards <invalid@invalid.invalid> - 2014-10-31 17:40 +0000
            Re: Classes Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-31 18:26 -0400
              Re: Classes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-01 12:09 +1100
      Re: Classes   Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-01 04:06 +1100
        Re: Classes   Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 13:18 -0400
          Re: Classes Rob Gaddi <rgaddi@technologyhighland.invalid> - 2014-10-31 10:43 -0700
            Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 14:18 -0400
              Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 14:42 -0400
              Re: Classes Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-31 18:57 -0400
                Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 19:22 -0400
                Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 19:32 -0400
                Re: Classes Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-11-01 12:00 -0400
                Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-11-01 12:42 -0400
                Re: Classes Denis McMahon <denismfmcmahon@gmail.com> - 2014-11-02 09:50 +0000
                Re: Classes Tim Delaney <timothy.c.delaney@gmail.com> - 2014-11-02 21:32 +1100
                Re: Classes Denis McMahon <denismfmcmahon@gmail.com> - 2014-11-02 12:27 +0000
                Re: Classes Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-11-02 11:31 -0500
                Re: Classes Denis McMahon <denismfmcmahon@gmail.com> - 2014-11-03 03:12 +0000
                Re: Classes Dan Sommers <dan@tombstonezero.net> - 2014-11-03 06:29 +0000
                Re: Classes Denis McMahon <denismfmcmahon@gmail.com> - 2014-11-04 01:10 +0000
                Re: Classes Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-11-04 18:30 +1300
                Re: Classes Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-11-03 08:50 -0500
                Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-11-04 02:34 +1100
                Re: Classes Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-03 07:47 -0700
                Re: Classes Larry Hudson <orgnut@yahoo.com> - 2014-11-02 14:03 -0800
            Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-11-01 07:51 +1100
              Re: Classes sohcahtoa82@gmail.com - 2014-10-31 14:24 -0700
                Re: Classes Rob Gaddi <rgaddi@technologyhighland.invalid> - 2014-10-31 14:40 -0700
                Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-11-01 08:56 +1100
                Re: Classes Chris Angelico <rosuav@gmail.com> - 2014-11-01 08:36 +1100
          Re: Classes Grant Edwards <invalid@invalid.invalid> - 2014-10-31 17:43 +0000
    Re: Classes Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-31 14:11 +0000
    Re: Classes   Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 12:49 -0400
      Re: Classes   "ast" <nomail@invalid.com> - 2014-10-31 19:31 +0100
        Re: Classes   Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 14:36 -0400
        Re: Classes Joel Goldstick <joel.goldstick@gmail.com> - 2014-10-31 14:41 -0400
          Re: Classes Seymore4Head <Seymore4Head@Hotmail.invalid> - 2014-10-31 14:56 -0400

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